* Linux
** Introduction
*** What are Linux distributions

There are various operating systems built upon GNU/Linux called Linux
distributions, each distribution adds additional, specific software, that allows
to cater the needs of a specific user group. Most of them are free. In this
course we'll use the Kali Linux distribution, it's based on another GNU/Linux
distribution called Debian.

*** Installing VirtualBox

We can install Kali as a main operating system, we can dual-boot (meaning we can
have both Linux, and another operating system installed at the same time), or we
can run Linux virtualised using VirtualBox.

The advantages is that if we damage the installation, we can just reinstall it,
or we can take snapshots, and come back to them at any times. We can easily
switch between operating systems, and we can even have several operating systems
running at the same time.

*What is VirtualBox?*, it's a free virtualisation software that allows you to
create and run virtual machines on your computer, it's developed by Oracle, and
it's free and open source software. To install it we must go to its website
[[https://www.virtualbox.org/wiki/Downloads]]. To run it, just download it, execute
the installer, press Next, Next, Next as necessary, and at the end press
Finish.

*** Installing Kali

To install kali, we must go to its website, press Download, press Virtual
Machines, and select VirtualBox. Once it's downloaded we have to extract it.

Once extracted, we have to press the "New" button, to create a new Virtual
Machine, we can give it a name, in our case it'll be Kali, then we will allocate
RAM and processors to it, as my pc allows me I'll give it 8GiB RAM and 4
processors, select "Use an existing virtual hard disk file", press the folder
icon, press the "Add" button and look for the vdi file that was downloaded
before.

Once chosen press Next, and finally press Finish. Now you can select the Kali
virtual machine, and press the "Start" button to run Kali.
